Unlocked at level 3, the Keep is the first building unlocked as building it allows the Player access to other buildings.
Ability: Produces a set amount of Gold every hour. Gold starts at 35 per hour and adds 10 more gold per Keep level. It is maxed its 225 gold per hour.The Keep can only store two hours worth of Gold at first, but can be increased through the Bank. The max level of the Keep, like all other buildings, is based on the level of the player. Then after level 20 you can increase buildings max level by 1 per 3 tiers gained. The costs after level 20 are capped but the cooldown times are not.

Level

Cost

1

50

2

400

3

1,350

4

3,200

5

6,250

6

10,800

7

17,150

8

25,600

9

36,450

10

50,000

11

66,550

12

86,400

13

109,850

14

137,200

15

168,750

16

204,800

17

245,650

18

291,600

19

342,950

20

400,000

Total

2,205,000

Note: First person to max at level 20 keep was skiloo on 16 Oct 2014.

Since v1.1 The builds caps were increase to level +floor(tier/3) giving you a building level every 3 tiers. This then maxes at tier 21 with level 27 being highest.